The present invention relates to stabilized radiopharmaceutical compositions containing radioactive iodine. It also includes within its scope a method for stabilizing the radiolytic decomposition of radiopharmaceutical compositions containing radioactive iodine.
Pharmaceutical compositions containing radioisotopes have many medical applications. These radiopharmaceuticals are useful as therapeutic agents or as diagnostic tools.
There are many commercially available radiopharmaceuticals containing isotopes such as iodine or cobalt useful in these applications. These preparations include for example I-131-ortho-Iodo-Hippuric Acid as a diagnostic tool for the determination of kidney function; Tc-99m Calcium Phytate Injection for renal and liver imaging and gold Au 198 injection for the treatment of neoplastic diseases and so on. Like all radioactive substances, these radiopharmaceuticals will undergo radiolytic decomposition as a result of spontaneous decay. Thus, for example .sup.123 I have a radiological half-life of 13.3 hours .sup.198 Au has a radiological half-life of about 2.7 days, and .sup.59 Fe has a radiological half-life of 45 days and so on. In order to decrease radiolytic decomposition, additives such as antioxidants, antibacterials and stabilizers have been incorporated in these compositions.
Antibacterial agents include for example mixtures of methylparaben and propylparaben; antioxidants include for example sodium bisulfite and sodium metabisulfite. Stabilizers to retard radiolytic decomposition include for example p-aminobenzoic acid, pyridoxine, pyridoal, ethyl gallate, propyl gallate and riboflavin-5-phosphate.
I have found that ascorbic acid, nicotinic acid or nicotinamide or their salts, amides, esters or complexes either alone or in combination when incorporated into radio pharmaceuticals containing radioactive iodine in a manner described below unexpectedly retard the radiolytic decomposition caused by radioactive decay of Iodine thereby prolonging their useful shelf-life.